title: Impaired phosphorylation and ubiquitination by p70 S6 kinase (p70S6K) and Smad ubiquitination regulatory factor 1 (Smurf1) promote tribbles homolog 2 (TRIB2) stability and carcinogenic property in liver cancer.
abstract: Tribbles homolog 2 (TRIB2) is critical for both solid and non-solid malignancies. Recently, TRIB2 was identified as a liver cancer-specific Wnt/β-catenin signaling downstream target and is functionally important for liver cancer cell survival and transformation. TRIB2 functions as a protein that interacts with E3 ubiquitin ligases and thereby modulates protein stability of downstream effectors. However, the regulation underlying TRIB2 protein stability per se has not yet been reported. In this study, we found that TRIB2 was up-regulated and exhibited high stability in liver cancer cells compared with other cells. We performed a structure-function analysis of TRIB2 and identified a domain (amino acids 1-5) at the N terminus that interacted with the E3 ubiquitin ligase Smurf1 and was critical for protein stability. Deletion of this domain extended TRIB2 half-life time accompanied with a more significant malignant property compared with wild type TRIB2. Furthermore, Smurf1-mediated ubiquitination required phosphorylation of TRIB2 by p70 S6 kinase (p70S6K) via another domain (amino acids 69-85) that is also essential for correct TRIB2 subcellular localization. Mutation of Ser-83 diminished p70S6K-induced phosphorylation of TRIB2. Moreover, the high stability of TRIB2 may be due to the fact that both p70S6K and Smurf1 were down-regulated and negatively correlated with TRIB2 expression in both liver cancer tissues and established liver cancer cell lines. Taken together, impaired phosphorylation and ubiquitination by p70S6K and Smurf1 increase the protein stability of TRIB2 in liver cancer and thus may be helpful in the development of diagnosis and treatment strategies against this malignant disease.
authors.affiliation: Department of Clinical Laboratory Medicine, Shanghai Tenth People's Hospital of Tongji University, 200072 Shanghai, China.
authors.forename: Jiayi
authors.initials: J
authors.lastname: Wang
authors.affiliation: Central Laboratory, Shanghai Tenth People's Hospital of Tongji University, 200072 Shanghai, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Clinical Laboratory Medicine, Shanghai Tenth People's Hospital of Tongji University, 200072 Shanghai, China.
authors.forename: Wenhao
authors.initials: W
authors.lastname: Weng
authors.affiliation: School of Public Health, Shanghai Jiaotong University School of Medicine, 200025 Shanghai, China.
authors.forename: Yongxia
authors.initials: Y
authors.lastname: Qiao
authors.affiliation: Department of Clinical Laboratory Medicine, Shanghai Tenth People's Hospital of Tongji University, 200072 Shanghai, China.
authors.forename: Lifang
authors.initials: L
authors.lastname: Ma
authors.affiliation: Central Laboratory, Shanghai Tenth People's Hospital of Tongji University, 200072 Shanghai, China.
authors.forename: Weifan
authors.initials: W
authors.lastname: Xiao
authors.affiliation: Central Laboratory, Shanghai Tenth People's Hospital of Tongji University, 200072 Shanghai, China.
authors.forename: Yongchun
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Central Laboratory, Shanghai Tenth People's Hospital of Tongji University, 200072 Shanghai, China. Electronic address: panqiuhui@263.net.
authors.forename: Qiuhui
authors.initials: Q
authors.lastname: Pan
authors.affiliation: Department of Clinical Laboratory Medicine, Shanghai Tenth People's Hospital of Tongji University, 200072 Shanghai, China. Electronic address: sunfenyong@126.com.
authors.forename: Fenyong
authors.initials: F
authors.lastname: Sun
mesh_terms: D017871:Calcium-Calmodulin-Dependent Protein Kinases; D015536:Down-Regulation / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D056945:Hep G2 Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation / Q000235:genetics; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000235:genetics; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000096:biosynthesis* / Q000235:genetics; D054875:Ubiquitination
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C498342:SMURF1 protein, human; D044767:Ubiquitin-Protein Ligases; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C489044:TRIB2 protein, human
keywords: E3 Ubiquitin Ligase; Gene Regulation; Hepatocellular Carcinoma; Phosphorylation; Post-translational Modification